I've always recorded analogue audio with Audition 3.0, but am getting the bug to record midi and use some VSTi plugins. According to this helpful doc from Adobe the process looks pretty straightforward: http://forums.adobe.com/message/1196432
Following this how-to to the letter, I have the Audition Polysynth showing in the Sequencer window. The left and right arrows are currently set to <all>. The problem is that I am hearing nothing when I click on the keys in the piano roll. All other audio plays fine from the system.
I double checked the Hardware Setup and am not seeing anything specific to MIDI. In my Windows 7 audio setup, MIDI audio output is set to the same audio device as analogue output (which works fine).
Right now I'm not worried about my MIDI keyboard/controller - I'm just trying to get sound from the piano roll in the Sequencer.